Surviving childhood cancer has its price.
Thirty years after their diagnosis, 40 percent of survivors have a serious health problem and a third have multiple problems, including stroke, heart disease and kidney failure, according to the largest study ever done on cancer survivors who have entered adulthood.
Only about one in three remain healthy.
"This is the dark side to being cured of cancer as a young person," said Philip Rosoff of the Duke University School of Medicine in a commentary in The New England Journal of Medicine, where the results will appear on Thursday.
The findings are a stark counterpoint to the stunning success of treating many childhood tumors. About 20,000 children are diagnosed with cancer in the United States each year and while most died 50 years ago, the cure rate is now greater than 75 percent.
Treatments blamed for later problems
Doctors have known for years that cancer treatments can spark new tumors later in life.
"It is now clear that damage to the organ systems of children caused by chemotherapy and radiation therapy may not become clinically evident for many years," said the research team, led by Kevin Oeffinger of the Memorial Sloan-Kettering Cancer Center in New York.
The new Childhood Cancer Survivor Study is based on data from 26 medical centers and marks the first large-scale attempt to assess other, long-term health problems.
"We've never looked at the big picture for pediatric cancer survivors," Oeffinger told Reuters. "While other studies looked at 200 or 300 people, we're looking at 10,000."
Comparing 10,397 survivors to 3,034 of their siblings, the researchers found that "cancer survivors were eight times as likely as their siblings to have severe or life-threatening chronic health conditions."
'Results are alarming'
Survivors of bone tumors, nerve and brain cancer, and Hodgkin's disease, a cancer of the immune system, faced the highest risk.
"By any criteria, these results are alarming," said Rosoff.
The survivors were 54 times more likely to have required a major joint replacement, 15 times more likely to have congestive heart failure or develop a second malignant tumor, 10 times more likely to have heart disease or thinking problems, and nine times more likely to have suffered a stroke or kidney failure.
The problems "run the gamut of affected organ systems, hinting that even more problems may cloud the future as this population ages," Rosoff said. Traditional age-related problems may hit this group even earlier than normal.
The source of the health problems varies.
Kidney failure, for example, may come from damage caused directly by chemotherapy or radiation, or from the multiple infections children can develop when cancer treatments hamper their immune system, Oeffinger said.
Drugs used to treat those infections may also play a role.
Today's kids may have different set of problems
The risk of stroke may become higher because head and chest radiation may cause premature thickening of the neck arteries, or changes in the heart valves can increase the risk that a clot will form, said Oeffinger.
Because cancer treatments have evolved since 1986, the last year the patients in this study were diagnosed with cancer, the next generation of survivors may have a "different array of long-term complications," both because some treatments have become more intense and doctors are more sensitive to the danger of late-in-life side effects, said Rosoff.